A computer-implemented method of a database statement for a relational database. The database comprises one or more tables comprising one or more data rows. A database statement is received. A set of predicates from the database statement and a set of data rows from the tables to use to generate the result of the database statement are determined. A set of interdiction statements applicable to one or more data rows is obtained. For each predicate, a set of masks applicable to one or more data rows is obtained, where for each mask, the data masked by the mask is used by the predicate. It is determined if a data row has an applicable interdiction statement, and contains data masked by a mask. If so, the result of the database statement without using the result of applying the predicate to the data row.